New research released at the International AIDS Conference in Amsterdam today is shedding light on several new promising HIV prevention tools, including the use of “on-demand” doses of Truvada, an HIV drug currently being used for pre-exposure prophylaxis (PrEP).

An ongoing study among men who have sex with men (MSM) in France has shown no new HIV infections among high-risk participants who opted for on-demand PrEP — a dosing protocol that differs from the daily regimen as currently advised in the U.S. and other countries. The same study also found that those who took PrEP daily also had no new HIV infections, confirming the results of several other past studies on the efficacy of the drug to reduce new HIV infections.

On-demand PrEP protocol involves taking a double dose of Truvada anywhere between two to 24 hours before sex, one dose 24 hours after sex and a second dose 48 hours after sex.

The French study also found other significant data points for HIV prevention workers. According to POZ:

The study authors found that those who chose daily PrEP tended to have more sexual partners and more frequent sex than those who opted for the on-demand strategy. There was also a trend toward increased sexual risk-taking over time among the participants. Given how highly effective Truvada is at preventing HIV acquisition, the word riskin this context largely applies to other sexually transmitted infections (STIs), including the bacterial infections gonorrhea, chlamydia and syphilis as well as hepatitis C virus (HCV).

The French researchers plan to continue enrolling new subjects in their study, conducted in the Paris region. The study began in May 2017 has enrolled 1,600 participants, with plans to expand to a total of 3,000 participants. By May 2020, researchers hope to show a 15 percent drop in annual HIV diagnoses in the Paris region.

Undetectable equals Untransmittable

Another study released at the international summit includes a long-awaited follow-up research examining the transmission risk between HIV-positive and HIV-negative same-sex male partners.

Advocates say it is yet more proof that an undetectable and virally suppressed HIV load effectively renders the virus noncontagious.

The “PARTNER2” study was a follow-up from a previous research effort that included primarily opposite-sex couples. Researchers expanded their study in order to examine the transmission risk between male couples.

The observational study found no new HIV transmissions among study partners, even after nearly 77,000 condomless anal sex acts. The study included nearly 1,000 gay male couples.

The PARTNER2 study mirrors similar results from the “Opposites Attract” study, which also found no new HIV transmissions between serodiscordant male couples.

For more on these studies, read this article from POZ.

Matt Comer previously served as editor from October 2007 through August 2015 and as a staff writer afterward in 2016.